1. Field of the Invention
This invention generally relates to methods and systems for determining design coordinates for defects detected on a wafer.
2. Description of the Related Art
The following description and examples are not admitted to be prior art by virtue of their inclusion in this section.
Inspection processes are used at various steps during a semiconductor manufacturing process to detect defects on wafers to promote higher yield in the manufacturing process and thus higher profits. Inspection has always been an important part of fabricating semiconductor devices. However, as the dimensions of semiconductor devices decrease, inspection becomes even more important to the successful manufacture of acceptable semiconductor devices because smaller defects can cause the devices to fail.
Accurately determining the location of a defect on a wafer is important for a number of reasons. In currently used approaches, defect location accuracy is limited due to inspection tool capability such as stage accuracy and run-time alignment. Relative to locations in design, a wafer coordinate system can be manually aligned to a design coordinate system by compensating for differences in offset, scale, and rotation. However, this approach does not address the errors coming from swath-related location errors. As a result, defect location accuracy (DLA) is limited to several times the inspection pixel being used even on advanced inspection tools.
The manual method described above has many disadvantages. For example, DLA is only improved by manually aligning the wafer coordinate system to the design coordinate system. The correction is typically limited to two sites for the whole wafer and therefore it lacks consideration for swath-based error. DLA error includes both inspection tool error and design-to-wafer alignment error, thereby limiting the DLA error to several multiples of inspection pixel size.
Accordingly, it would be advantageous to develop systems and/or methods that do not have one or more of the disadvantages described above.